diff --git a/lib/redmine/access_control.rb b/lib/redmine/access_control.rb
index 76c9906b1..2642e9b95 100644
--- a/lib/redmine/access_control.rb
+++ b/lib/redmine/access_control.rb
@@ -84,6 +84,7 @@ module Redmine
 
       def permission(name, hash, options={})
         @permissions ||= []
+        @permissions.reject! {|p| p.name == name}
         options[:project_module] = @project_module
         @permissions << Permission.new(name, hash, options)
       end
diff --git a/lib/redmine/menu_manager.rb b/lib/redmine/menu_manager.rb
index 0ff2bfd71..be1992709 100644
--- a/lib/redmine/menu_manager.rb
+++ b/lib/redmine/menu_manager.rb
@@ -296,6 +296,8 @@ module Redmine
           target_root = @menu_items.root
         end
 
+        target_root.children.reject! {|item| item.name == name}
+
         # menu item position
         if first = options.delete(:first)
           target_root.prepend(MenuItem.new(name, url, options))
@@ -383,8 +385,6 @@ module Redmine
 
       # Adds a child at given position
       def add_at(child, position)
-        raise "Child already added" if find {|node| node.name == child.name}
-
         @children = @children.insert(position, child)
         child.parent = self
         child
diff --git a/lib/redmine/plugin.rb b/lib/redmine/plugin.rb
index fb42a8fa9..dacafb315 100644
--- a/lib/redmine/plugin.rb
+++ b/lib/redmine/plugin.rb
@@ -125,14 +125,6 @@ module Redmine
       # Warn for potential settings[:partial] collisions
       if p.configurable?
         partial = p.settings[:partial]
-        if @used_partials[partial]
-          Rails.logger.warn(
-            "WARNING: settings partial '#{partial}' is declared in '#{p.id}' plugin " \
-              "but it is already used by plugin '#{@used_partials[partial]}'. " \
-              "Only one settings view will be used. " \
-              "You may want to contact those plugins authors to fix this."
-          )
-        end
         @used_partials[partial] = p.id
       end
 
diff --git a/lib/redmine/scm/base.rb b/lib/redmine/scm/base.rb
index 1a3fabf61..c65098977 100644
--- a/lib/redmine/scm/base.rb
+++ b/lib/redmine/scm/base.rb
@@ -11,6 +11,7 @@ module Redmine
         # Add a new SCM adapter and repository
         def add(scm_name)
           @scms ||= []
+          @scms.delete(scm_name)
           @scms << scm_name
         end
 
diff --git a/lib/redmine/wiki_formatting.rb b/lib/redmine/wiki_formatting.rb
index 09fc4d3d7..08f322143 100644
--- a/lib/redmine/wiki_formatting.rb
+++ b/lib/redmine/wiki_formatting.rb
@@ -34,7 +34,6 @@ module Redmine
       def register(name, *args)
         options = args.last.is_a?(Hash) ? args.pop : {}
         name = name.to_s
-        raise ArgumentError, "format name '#{name}' is already taken" if @@formatters[name]
 
         formatter, helper, parser =
           if args.any?